Several whole-body disorders produce changes in the skin. In some instances, the skin changes are characteristic of the particular disease. Often, however, the signs are not obviously associated with the underlying condition and must be carefully differentiated from primary skin disorders. Some of these secondary disorders are mentioned briefly below and are also described in the chapters on the specific disorders.
Skin disorders can be associated with nutritional deficiencies, especially of proteins, fats, minerals, some vitamins, and trace elements. However, this is uncommon in dogs fed modern, balanced diets. Siberian Huskies, and occasionally other breeds, may require additional zinc in their diet. Consult your veterinarian regarding your pet’s dietary needs to avoid health problems related to nutritional deficiencies.
Dermatitis (inflammation of the skin) is sometimes seen in association with disorders of internal organs, such as the liver, kidneys, or pancreas. Liver disease and diabetes can cause superficial skin tissue death (necrolytic dermatitis) in old dogs. The signs of these skin abnormalities include redness, crusting, oozing, and hair loss of the footpads, face, genitals, and lower legs. The skin disease may precede the onset of signs of the internal disease. Any ongoing or growing abnormality of the skin of your dog should be examined by your veterinarian. Early diagnosis of disease offers the best chance for effective treatment for your pet.
A generalized lumpy skin syndrome in German Shepherds, and occasionally other breeds, is associated with kidney cysts. Poisoning by rat poison, ergot (a fungus found in rye and other grains), mercury, and iodides may cause various skin changes. In male dogs with testicular tumors, widespread hair loss and occasional itching with a skin rash may be seen. Nonspayed female dogs with hormonal imbalances are usually itchy and have skin rashes, mammary tissue enlargement, and frequent estrous cycles. The skin tumors of both disorders may begin in the groin or flank region and progress toward the head.
Hypothyroidism can cause skin changes with diminished hair growth and hair loss. The skin is dry, scaly, thickened, and folded. Secondary bacterial infection may occur. The edges of the ears may develop excess scale. Hypopituitarism is a congenital disease characterized by short stature and hair loss. Hyperadrenocorticism (an increase in the activity of the adrenal glands; also called Cushing disease) also causes skin changes, such as darkening of skin color, hair loss, seborrhea (oily dandruff), calcium deposits in the skin, and secondary bacterial infection.
Rarely, underlying nervous system disorders can result in skin changes. Signs generally include scratching (sometimes "air scratching"), pain, or self-injury.
Treatment of all these conditions depends on finding the specific cause. Once this is established and managed, the skin usually needs only symptomatic care, such as control of scratching, until it returns to normal with resolution of the primary disease.
Also see professional content regarding systemic dermatoses.